Nonsurgically recovered baboon embryos will be cultured to determine the stage of post-implantation development that can be achieved in vitro. Culture media collected at least daily from prehatched embryos at similar cleavage stages will be pooled to determine the temporal initiation of baboon chorionic gonadotropin (bCG) secretion. The existence of a relationship between an individual embryo's post-hatching bCG production and developmental achievement will be investigated. Culture media alterations will be made to define metabolic requirements for maximum in vitro development. Embryos will be fixed and sectioned to determine the exact developmental stage achieved, which will be compared chronologically with published observations on in vivo development in the baboon. In an attempt to maximize the number of embryos available from each baboon and to allow embryos to be separated into different treatment groups, the capability of baboon ovaries to respond to various hormone treatments with multiple follicle growth and ovulation will be tested. This study will provide valuable information about early embryonic development in a primate species that has phylogenetic proximity to humans, and has the potential of establishing the culture system as an efficient method for determining the effects of various pharmacological agents, including contraceptives and potential teratogens, on embryo growth and viability.